21395509399 has 4 divisors (see below), whose sum is σ = 23340555720. Its totient is φ = 19450463080.

The previous prime is 21395509361. The next prime is 21395509453. The reversal of 21395509399 is 99390559312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21395509399 - 2¹³ = 21395501207 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21395504399) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 972523144 + ... + 972523165.

It is an arithmetic number, because the mean of its divisors is an integer number (5835138930).

Almost surely, 2^21395509399 is an apocalyptic number.

21395509399 is a deficient number, since it is larger than the sum of its proper divisors (1945046321).

21395509399 is a wasteful number, since it uses less digits than its factorization.

21395509399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1945046320.

The product of its (nonzero) digits is 2952450, while the sum is 55.

The spelling of 21395509399 in words is "twenty-one billion, three hundred ninety-five million, five hundred nine thousand, three hundred ninety-nine".